CN102442975B - A kind of method of olefin epoxidation - Google Patents

Abstract

The invention provides a method for olefin epoxidation, which comprises the step of making olefin and hydrogen peroxide carry out epoxidation reaction in the presence of catalyst and basic anion exchange resin under the condition of olefin epoxidation reaction. By adopting the method provided by the invention to synthesize epoxidized olefin, the conversion rate of hydrogen peroxide, the selectivity of epoxidized olefin and the service life of the catalyst can be significantly improved.

Description

A kind of method of olefin epoxidation

technical field

The invention relates to a method for epoxidation of olefins.

Background technique

Propylene oxide is the third largest organic chemical product in the production of propylene derivatives after polypropylene and acrylonitrile. It is mainly used to produce polyether, propylene glycol, isopropanolamine, non-polyether polyols, etc., and then to produce unsaturated Polyester resin, polyurethane, surfactant, flame retardant and other important raw materials.

The traditional preparation methods of propylene oxide mainly include chlorohydrin method and co-oxidation method. When the chlorohydrin method is used to synthesize propylene oxide, the equipment is seriously corroded, consumes a large amount of Cl ₂ , produces a large amount of waste water and waste residue, and causes great pollution to the environment. With the increasing requirements for environmental protection, this process will eventually be eliminated. Elimination; while the co-oxidation method has a long process and a large investment, and the production is restricted by the use of by-product outlets. Therefore, these traditional propylene oxide preparation methods restrict the production of propylene oxide.

In order to overcome the defects of the above-mentioned traditional preparation of propylene oxide, a new synthesis process has been developed, which uses hydrogen peroxide as the oxidant and titanium silicon molecular sieve as the catalyst to catalyze the epoxidation of propylene to prepare propylene oxide . The process has the advantages of mild conditions, environmentally friendly and pollution-free process, and meets the requirements of the development concept of green chemistry and atomic economy. Therefore, this process has become the development trend of the process for preparing propylene oxide.

In the process of synthesizing propylene oxide with hydrogen peroxide as oxidant and titanium silicon molecular sieve as catalyst, the pH value in the reaction system is one of the most critical technical parameters in the whole process. Usually, because H ₂ O ₂ is acidic, therefore, the pH value of the reaction system is small without adding a pH value regulator, and the reactivity in the reaction system is low at this time, resulting in low production efficiency; and when When the pH value in the reaction system is too high (such as the pH value being more than 9), it will cause the occurrence of side reactions and reduce the selectivity of propylene oxide; at the same time, hydrogen peroxide decomposes very quickly, thereby reducing the utilization rate of hydrogen peroxide.

For this reason, those skilled in the art have tried to add substances to adjust the pH value in the reaction system, so as to control the pH value of the reaction system within an appropriate range.

For example, US 5675026 discloses a process for the preparation of epoxides from olefins and hydrogen peroxide in the presence of a zeolite containing titanium atoms as a catalyst, which involves adding a neutral or acidic reactive salt to the catalyst before or during the reaction . US 6300506 discloses a method for directly epoxidizing olefins to prepare olefin oxides with hydrogen peroxide or a compound capable of generating hydrogen peroxide under reaction conditions, wherein the epoxidation reaction is carried out in the presence of a catalyst system, the catalyst The system is composed of titanium-containing zeolite and a buffer system for controlling the pH value at 5.0-8.0, and the buffer system is composed of nitrided alkali and salt of nitrided alkali and organic or inorganic acid. However, the substances to adjust the pH value added to the epoxidation reaction system in the above two patents may lead to the formation of nascent oxygen in the reaction system. The nascent oxygen has high activity and poor oxidation selectivity, resulting in The local reaction is severe, the side reaction is increased, the selectivity of propylene oxide is reduced, and the by-products produced will lead to a significant reduction in the service life of the catalyst.

Contents of the invention

The present invention provides a kind of new method for olefin epoxidation in order to overcome the above-mentioned defect of existing propylene epoxidation process, in the process that adopts this method to prepare epoxidized olefin, the conversion rate of hydrogen peroxide and the epoxidation The selectivity of olefin oxide is higher, and the service life of the catalyst is longer.

The invention provides a method for olefin epoxidation, which comprises the step of making olefin and hydrogen peroxide carry out epoxidation reaction in the presence of catalyst and basic anion exchange resin under the condition of olefin epoxidation reaction.

According to the method for the epoxidation of olefins provided by the present invention, the basic anion exchange resin can undergo an ion exchange reaction with hydrogen ions in the reaction system of olefins and hydrogen peroxide, so as to appropriately increase the pH value in the reaction system, And the pH value in the reaction system can be kept from being too high. Therefore, adopt the described method that the present invention provides to synthesize epoxidized olefin, test result shows that hydrogen peroxide invalid decomposition is less, and the selectivity that reaction generates epoxidized olefin is better, and the by-product that side reaction generates is less, thereby can Significantly improve the conversion rate of hydrogen peroxide, the selectivity of epoxidized olefins and the service life of the catalyst. The reason may be due to the presence of the basic anion exchange resin on the one hand, which can inhibit the nascent oxygen in the decomposition process of hydrogen peroxide. On the other hand, the ion exchange reaction between hydrogen ions and basic anion exchange resin in the reaction system is relatively gentle, so that the occurrence of side reactions can be effectively suppressed.

Detailed ways

The olefin epoxidation method provided by the invention comprises the steps of epoxidizing olefin and hydrogen peroxide in the presence of a catalyst and a basic anion exchange resin under olefin epoxidation reaction conditions.

According to the method for the olefin epoxidation provided by the present invention, the total exchange capacity of the basic anion exchange resin can be 0.5-3mmol/ml, preferably 0.8-2.5mmol/ml, more preferably 1.1-1.6mmol/ml ml. The proportion of the catalyst and the basic anion exchange resin is not particularly limited, as long as the amount of the basic anion exchange resin can adjust the pH of the reaction system to 3-9, preferably 4-8. However, in the actual production process, when the amount of the basic anion exchange resin is relatively too low (such as the weight ratio of the catalyst to the basic anion exchange resin is greater than 1:0.05), the basic anion exchange The effect of adjusting the pH value of the resin is very weak, thereby can not obviously improve the conversion rate of hydrogen peroxide, the selectivity of epoxidized olefin and the service life of catalyst; And when the consumption of described basic anion exchange resin is relatively too high (as When the weight ratio of the catalyst to the basic anion exchange resin is less than 1:1.5), the relative content of the catalyst in the system of the epoxidation reaction is too low, resulting in a reaction in the reaction system The speed is very low. Therefore, in the present invention, the weight ratio of the catalyst to the basic anion exchange resin is preferably 1:0.05-1.5, more preferably 1:0.1-1, even more preferably 1:0.2-0.8. In this case, due to the ion exchange between the basic anion exchange resin and the hydrogen ions in the reaction system, the pH value in the epoxidation reaction system can be stably controlled in the range of 4-8, so that The epoxidation reaction in the reaction system can be carried out smoothly without causing local reactions to be too violent, and can effectively inhibit the decomposition of hydrogen peroxide and the occurrence of side reactions, improve the selectivity of epoxidation products, and simultaneously The service life of the catalyst is also increased due to fewer side reactions. In the present invention, the total exchange capacity refers to the total amount of all exchangeable groups in a unit volume of ion exchange resin.

In the present invention, the basic anion exchange resin may be various basic anion exchange resins known in the art, including strongly basic anion exchange resins and/or weakly basic anion exchange resins. Further, the basic anion exchange resin may be, for example, a styrene-based basic anion-exchange resin and/or an acrylic-based basic anion-exchange resin. The basic anion exchange resin can be macroporous or gel-type, preferably macroporous. The basic anion exchange resin is commercially available, for example, from Anhui Sanxing Resin Co., Ltd.

In the present invention, the type of the catalyst is not particularly limited, and can be properly selected from various catalysts conventionally used in the olefin epoxidation process, for example, it can be a titanium-silicon molecular sieve catalyst, a modified titanium-silicon molecular sieve catalyst Or their mixture, and heteropolyacid catalyst etc. Preferably, the catalyst is a titanium-silicon molecular sieve catalyst, specifically, the titanium-silicon molecular sieve can be, for example, a titanium-silicon molecular sieve with an MFI structure, a titanium-silicon molecular sieve with a MEL structure, a titanium-silicon molecular sieve with a BETA structure, and a ZSM-12 type At least one of titanium-silicon molecular sieves. Generally, the structural formula of the titanium-silicon molecular sieve is: xTiO ₂ ·SiO ₂ , wherein x may be 0.0001-0.04, preferably 0.01-0.03. In the present invention, the titanium-silicon molecular sieve can be obtained commercially or can be prepared. The method for preparing the titanium-silicon molecular sieve is known to those skilled in the art. For example, it can be prepared by the method for preparing a catalyst disclosed in CN101279959A have to. In order to further improve the conversion rate of hydrogen peroxide and the selectivity of epoxidized olefins in the olefin epoxidation process, the catalyst is more preferably a titanium-silicon molecular sieve with a crystal grain of a hollow structure, and the diameter of the cavity part of the hollow structure The longitudinal length is 5-300 nanometers, and the benzene adsorption capacity of the titanium-silicon molecular sieve measured under the conditions of 25°C, P/P ₀ =0.10, and adsorption time of 1 hour is at least 70 mg/g. The titanium-silicon molecular sieve There is a hysteresis loop between the adsorption isotherm and desorption isotherm of low temperature nitrogen adsorption. In the olefin epoxidation method provided by the present invention, when the catalyst is more preferably a titanium-silicon molecular sieve with hollow grains, the reaction raw materials can easily enter the cavity part of the catalyst and the titanium-silicon molecular sieve The active components contact and react, thereby further enhancing the activity of the catalyst; at the same time, the epoxidized olefin as the epoxidation product can also easily fall off from the active site of the titanium-silicon molecular sieve, and then diffuse into the cavity of the titanium-silicon molecular sieve Among them, the residence time of epoxidized olefins on the active sites of titanium-silicon molecular sieves is shortened, and the probability of side reactions of epoxidized olefins is further reduced, thereby further improving the selectivity of epoxidized reactions.

According to the olefin epoxidation method provided by the present invention, the epoxidation reaction can be carried out in the presence of an organic solvent. In the case where the epoxidation reaction is carried out in the presence of an organic solvent, the molar ratio of the organic solvent, olefin and hydrogen peroxide is preferably (4-15):(0.5-5):1, more preferably (5-12):(1-3):1, more preferably (5-10):(1.5-2.5):1.

In the present invention, the olefin is not particularly limited, for example, it may be an olefin with 3-8 carbon atoms, specifically, the olefin may be one of propylene, butene and pentene, preferably propylene. The type of the solvent is not particularly limited in the present invention, for example, it can be at least one of C1-C6 alcohol and C2-C6 nitrile, preferably at least one of methanol, ethanol, propanol, butanol and acetonitrile , preferably methanol. The hydrogen peroxide is usually used in the form of an aqueous solution, and the concentration of the hydrogen peroxide may be 10-70% by weight, preferably 20-50% by weight.

The condition of described olefin epoxidation reaction can be the conventional reaction condition of this reaction, the present invention has no special limitation to it, yet, in order to obtain the conversion ratio of suitable hydrogen peroxide and the selectivity of epoxidized olefin, described The conditions of the olefin epoxidation reaction preferably include: a temperature of 30-90° C., more preferably 40-80° C.; a pressure of 0.5-4.5 MPa, more preferably 0.6-3 MPa.

The method for the olefin epoxidation provided by the present invention can be implemented in various conventional reactors, and the reactor can include at least one of fixed bed reactors, moving bed reactors, slurry bed reactors, etc. A sort of. In the case that the method is implemented in a fixed bed reactor, a moving bed reactor or a continuous slurry bed reactor, the conditions of the olefin epoxidation reaction may also include a liquid volume space velocity of 1-15h ^-1 , preferably 2-10h ^-1 . In the case where the method is implemented in a batch reactor, the conditions of the olefin epoxidation reaction may also include: based on the total weight of the olefin and hydrogen peroxide being 100 parts by weight, the catalyst and The total amount of basic anion exchange resin used is 3-10 parts by weight, preferably 4-9 parts by weight, and the reaction time can be 0.2-3 hours.

In the present invention, the fixed bed reactor, moving bed reactor and slurry bed reactor can be implemented by using various corresponding types of reactors conventionally used in the art. In the present invention, the fixed bed reactor is the most widely used reactor in the industry, and refers to the equipment that the fluid reacts through the bed level formed by immobile solid materials; the slurry bed reactor is also called slurry state The bed reactor refers to the reactor in which tiny solid particles of the catalyst are suspended in the liquid medium. In the slurry bed reactor, the material is back mixed. The moving bed reactor is a reactor used to realize the continuous feeding and discharging of gas-solid phase reaction process or liquid-solid phase reaction process, and the material backmixing of the moving bed reactor is very small. The process of the invention is preferably carried out in a fixed bed reactor.

The present invention will be further described below through embodiment. In the following examples, the calculation method of the conversion rate of the hydrogen peroxide and the selectivity of propylene oxide is as follows:

The conversion rate of hydrogen peroxide = the number of moles of converted hydrogen peroxide/the number of moles of hydrogen peroxide fed × 100%

The selectivity of propylene oxide = the number of moles of propylene oxide produced / the sum of the total number of moles of epoxides produced × 100%

Wherein, the detection method of the molar number of hydrogen peroxide, the molar number of propylene oxide and the total molar number of the epoxides of generation are known to those skilled in the art, for example, the molar number of hydrogen peroxide can adopt iodometric method to detect , the molar number of propylene oxide and the total molar number of epoxides can be detected by chromatographic internal standard method.

Preparation Example 1: Preparation of Ti-Si Molecular Sieve Catalyst

100 grams of titanium-silicon molecular sieve powder (purchased from Hunan Jianchang Co., Ltd., brand HTS), 1 gram of magnesium oxide and 40 grams of tetramethoxysilane are mixed uniformly, and then 20 grams of silica sol (SiO The content of ₂ is 30% by weight), 2 grams of polyvinyl alcohol, 1 gram of Sesame powder (purchased from Dongming County Zhuwa Tianjing Glue Factory) and 20 milliliters of water, mixed evenly and extruded into strips, the size is 2 ×2 mm, and then dried at 70° C. for 4 hours to obtain molding A.

Take 100 grams of molding A and put it into a three-necked bottle, add 200ml of 20% by weight sodium hydroxide solution, heat to 90°C and keep it warm for 6 hours, then wash with deionized water until the washing water does not contain sodium ions until. Then, it was dried at 120°C for 3 hours, and fired at 550°C for 3 hours to obtain a fired product B.

Get 100 grams of roasted product B and put it into a three-necked flask, add 200ml concentration of 20% by weight sodium hydroxide solution and 10ml concentration of 27.5% by weight hydrogen peroxide solution, reflux heating at 90°C for 2 hours, and then use Wash with deionized water until the washing water is free of sodium ions. Finally, it was dried at 120° C. for 3 hours and calcined at 550° C. for 5 minutes to prepare the titanium-silicon molecular sieve catalysts used in the examples and comparative examples of the present invention.

Example 1

This example is used to illustrate the method for epoxidation of olefins provided by the present invention.

The titanium-silicon molecular sieve catalyst prepared in Preparation Example 1 and the macroporous strongly basic styrene-based anion exchange resin (purchased from Anhui Sanxing Resin Co., Ltd., with a total exchange capacity of 1.5mmol/ml) were carried out at a weight ratio of 1:1. Mix, and pack in fixed-bed reactor (purchased from Penglai Luhao Chemical Machinery Co., Ltd., hereinafter the same), the filling capacity is 15 milliliters, forms catalyst bed in described fixed-bed reactor, in described catalyst bed Install the ceramic ring packing on the top and bottom respectively.

Then, at 60°C, the molar ratio of methanol, propylene and hydrogen peroxide is 6:2:1, and the reactant is injected into the fixed-bed reactor at a liquid volume space velocity of 7h ^-1 to maintain the fixed-bed reactor. The pressure in the reactor is 2.5MPa, and make described fixed-bed reactor run continuously 1700 hours, in the process that described fixed-bed reactor is running, detect and calculate hydrogen peroxide conversion rate and propylene oxide selectivity intermittently , and the results are shown in Table 1 below.

Table 1

Response time/hour Conversion rate of hydrogen peroxide (%) Propylene oxide selectivity (%) 17.00 89.25 99.55 200.00 93.25 97.56 700.00 92.00 97.50 1206.00 92.10 97.23 1700.00 90.70 97.98

Comparative example 1

Carry out according to the method for embodiment 1, difference is, the catalyst bed layer that is loaded into described fixed-bed reactor does not comprise macroporous strongly basic styrenic anion exchange resin, and preparation example 1 with the same weight The titanium-silicon molecular sieve catalyst prepared in the paper replaces the macroporous strongly basic styrene-based anion exchange resin. The hydrogen peroxide conversion rate and propylene oxide selectivity detected and calculated during the operation of the fixed-bed reactor are shown in Table 2 below.

Table 2

Response time/hour Conversion rate of hydrogen peroxide (%) Propylene oxide selectivity (%) 17.00 90.85 93.45 200.00 85.25 91.28 300.00 75.69 83.04 406.00 65.56 71.32 521.00 54.18 60.67

Example 2

This example is used to illustrate the method for epoxidation of olefins provided by the present invention.

The titanium-silicon molecular sieve catalyst prepared in Preparation Example 1 and the macroporous strongly basic styrene-based anion exchange resin (purchased from Anhui Sanxing Resin Co., Ltd., with a total exchange capacity of 1.3mmol/mL) were carried out at a weight ratio of 1:0.1 Mixed and packed into a fixed-bed reactor with a loading capacity of 15 milliliters, a catalyst bed was formed in the fixed-bed reactor, and ceramic ring fillers were respectively placed above and below the catalyst bed.

Then, at 40° C., the molar ratio of ethanol, propylene and hydrogen peroxide is 5:1.5:1 and the reactant is injected into the fixed bed reactor at a liquid volume space velocity of ¹⁰ h to maintain the fixed bed reactor. The pressure in the reactor is 1MPa, and the fixed-bed reactor is continuously operated for 1700 hours. During the operation of the fixed-bed reactor, the hydrogen peroxide conversion rate and propylene oxide selectivity are intermittently detected and calculated. , and the results are shown in Table 3 below.

table 3

Response time/hour Conversion rate of hydrogen peroxide (%) Propylene oxide selectivity (%) 17.00 85.35 99.45 200.00 92.15 97.86 700.00 91.00 97.57 1206.00 90.00 97.58 1700.00 90.10 96.75

Comparative example 2

Carry out according to the method for embodiment 2, difference is, in the catalyst bed layer that is loaded into the described fixed-bed reactor, with the same weight Na ₂ HPO ₄ replace macroporous strongly basic styrenic anion exchange resin. The hydrogen peroxide conversion rate and propylene oxide selectivity were calculated and detected during the operation of the fixed-bed reactor, and the results are shown in Table 4 below.

Table 4

Response time/hour Conversion rate of hydrogen peroxide (%) Propylene oxide selectivity (%) 17.00 85.35 99.35 200.00 90.15 97.74 300.00 89.00 92.53 406.00 81.00 84.36 508.00 75.10 79.65

Example 3

This example is used to illustrate the method for epoxidation of olefins provided by the present invention.

Mix the titanium-silicon molecular sieve catalyst prepared in Preparation Example 1 with the macroporous strongly basic acrylic anion exchange resin (purchased from Hangzhou Zhengguang Resin Co., Ltd., with a total exchange capacity of 1.5 mmol/mL) at a weight ratio of 1:0.5 , and packed into a fixed-bed reactor with a loading capacity of 15 milliliters. A catalyst bed was formed in the fixed-bed reactor, and ceramic ring fillers were respectively installed up and down the catalyst bed.

Then, at 80° C., the molar ratio of acetonitrile, propylene, and hydrogen peroxide is 10:2.5:1, and the reactant is injected into the fixed-bed reactor at a liquid volume space velocity of ² h to maintain the fixed-bed reactor. The pressure in the reactor is 3MPa, and the fixed-bed reactor is continuously operated for 1700 hours. During the operation of the fixed-bed reactor, the hydrogen peroxide conversion rate and propylene oxide selectivity are intermittently detected and calculated. , and the results are shown in Table 5 below.

table 5

Response time/hour Conversion rate of hydrogen peroxide (%) Propylene oxide selectivity (%) 17.00 89.35 99.45 200.00 90.15 98.85 700.00 91.00 97.87 1206.00 90.50 97.85 1700.00 91.10 97.75

Example 4

This example is used to illustrate the method for epoxidation of olefins provided by the present invention.

Titanium-silicon molecular sieve powder (purchased from Hunan Jianchang Co., Ltd., brand HTS) and gel-type strongly basic styrene-based anion exchange resin (purchased from Shandong Dongda Chemical Industry Co., Ltd., with a total exchange capacity of 1.3mmol/mL ) are mixed with a weight ratio of 1:1, and are continuously added from the top of the moving bed reactor (purchased from Chengdu Xindu Yongtong Machinery Factory), and simultaneously the titanium-silicon molecular sieve catalyst and the gel-type strong base The mixture of permanent styrenic anion exchange resin is continuously discharged from the bottom of the reactor and circulated to the top of the reactor to ensure the filling of the mixture of titanium silicon molecular sieve catalyst and gel type strong basic styrenic anion exchange resin in the reactor The amount is 15 milliliters; And, the reactant that the molar ratio of methanol, propylene and hydrogen peroxide is 6: 2: 1 is injected wherein with the liquid volume space velocity of 7h ^-1 from the bottom of described moving bed reactor, and The temperature in the reactor was maintained at 60° C. and the pressure at 2.5 MPa. The fixed-bed reactor was operated continuously for 1700 hours. During the operation of the fixed-bed reactor, the hydrogen peroxide conversion rate and propylene oxide selectivity were intermittently detected and calculated. The results are shown in Table 6 below.

Table 6

Response time/hour Conversion rate of hydrogen peroxide (%) Propylene oxide selectivity (%) 17.00 88.25 99.40 200.00 90.05 98.95 700.00 91.05 97.87 1206.00 90.35 97.84 1700.00 91.05 97.65

As can be seen from the data in Tables 1-6, in Examples 1-4, when the reactor was operated continuously for 1700 hours, the hydrogen peroxide conversion rate and propylene oxide selectivity still remained above 90%, indicating that Now catalyst still keeps good activity; And in comparative example 1 and 2, when described reactor runs continuously below 550 hours, described hydrogen peroxide conversion rate and propylene oxide selectivity all drop below 80%, show At this time, the activity of the catalyst is significantly reduced. This shows, adopt described method provided by the present invention to synthesize propylene oxide, make the catalyst used can keep good activity for a long time and can not be deactivated, and, in the process of synthesizing propylene oxide, keep high all the time Hydrogen peroxide conversion and propylene oxide selectivity.

Claims (11)

1. an olefin epoxidation method, it is characterized in that, the method is included under epoxidation reaction of olefines condition, make alkene and hydrogen peroxide under the existence of catalyzer and basic anion exchange resin, carry out epoxidation reaction, the weight ratio of described catalyzer and described basic anion exchange resin is 1:0.05-1.5.

2. method according to claim 1, wherein, the weight ratio of described catalyzer and described basic anion exchange resin is 1:0.1-1.

3. method according to claim 2, wherein, the total exchange capacity of described basic anion exchange resin is 0.5-3mmol/ml.

4. method according to claim 1, wherein, described epoxidation reaction is carried out under the existence of solvent, and described solvent is the alcohol that acetonitrile and/or carbonatoms are 1-6.

5. method according to claim 4, wherein, the mol ratio of described solvent, alkene and hydrogen peroxide is (4-15): (0.5-5): 1.

6. method according to claim 1, wherein, described catalyzer is for take the catalyzer that HTS is active component.

7. method according to claim 6, wherein, the crystal grain of described HTS is hollow structure, the radical length of the cavity part of this hollow structure is 5-300 nanometer, and described HTS is at 25 ℃, P/P ₀=0.10, adsorption time is that the benzene adsorptive capacity recording under the condition of 1 hour is at least 70 milligrams/grams, between the adsorption isothermal line of the nitrogen absorption under low temperature of this HTS and desorption isotherm, has hysteresis loop.

8. method according to claim 1, wherein, described alkene is that carbonatoms is the alkene of 2-8.

9. method according to claim 8, wherein, described alkene is propylene.

10. method according to claim 1, wherein, described epoxidation reaction of olefines condition comprises: temperature is 30-90 ℃, pressure is 0.5-4.5MPa.

11. methods according to claim 1, wherein, described epoxidation reaction is carried out in fixed-bed reactor.